Dull bit indicator



W. J. BIELSTEIN DULL BIT INDICATOR Filed June 15, 1949 July 10, 1951 ATTORNEY.

Patented July 10, 1951 Dom. err INDICATOR Walter J. Bielstein, Houston, Tex., assignor, by

mesne assignments, to Standard Oil Development Company, Elizabeth, N. J., a corporation of Delaware Application June 15, 1949, Serial No. 99,249

'7 Claims.

This invention relates to a drill bit used for drilling boreholes into Subsurface formations. More particularly, this invention relates to a drill bit which, when it is worn by a pre-determined amount during drilling operations, will give a signal of such wear at the surface of the earth.

In the drilling of boreholes into subsurface formations by the rotary drilling method, particularly in drilling boreholes for the production of minerals, such as oil and gas, the drill bit attached to the end of the drill stem is subjected to conditions which cause rapid wear of the cutting edges of the bit blades. The blades of several bits are ordinarily worn off in drilling such a well. Of course, when the blades are worn off a particular bit, the drilling crew must pull the drill stem out of the hole and replace the worn bit with a new bit before resuming drilling operations. When conventional bits are employed in such operations, no positive method is available for determining the point when the cutting blades of the drill bit are worn to such an extent as to require replacement of the bit; consequently, the selection of the time when the drill bit should be removed from the hole is wholly within the judgment of the drilling crew. As would be expected, conventional drill bits are sometimes removed from the hole before the blades have been worn to the point where the drill bit should really be replaced. n the other hand, and perhaps more commonly, the drill stem is sometimes not withdrawn from the hole and the bit replaced until long after the blades have been worn to such an extent that little or no hole is being made. As a matter of fact, drilling is sometimes continued until the bit blades have been completely worn off the bit body and the bit body itself damaged by wear.

Although excessive wear of the cutting edge of the bit blades is the most frequent reason for replacement of conventional drill bits, it sometimes happens that the bit should be replaced because it has become worn out of gauge. Here again the drilling crew has no positive means of knowing when the bit has become so worn. A drill bit is said to be worn out of gauge when the reaming edges of the bit blades have been worn to such an extent that the diameter of the hole being made is smaller than may conveniently be tolerated. For example, the diameter of a hole drilled with a bit having worn reaming edges may not be sufiiciently great to permit the free passage of a new unworn drill bit subsequently introduced into the hole. When this condition exists, the borehole walls must be enlarged by reaming in a suitable manner as with a, new bit. Not only does reaming consume time but it also entails the risk of a stuck drill bit.

It is an object of this invention to provide a drill bit which, when worn by a pre-determined amount, will cause an increase in fluid pressure in the mud stream used with the drill string and thus give a signal to the drilling screw indicating that the drill bit should be removed because of excessive wear.

It is a further object to. provide a drill bit, the body of which will not be damaged during drilling operations and in which the construction is such that repair of the used bit is convenient and simple.

The foregoing objects, as well as other advantages, are attained by the present invention as will be apparent from the following detailed description taken in connection with the accompanying drawings in which Fig. l is a front view, partly in cross section, of a drill bit constructed in accordance with the present invention with the parts thereof in their relative positions during normal drilling and before the bit blades have become excessively worn;

Fig. 2 is a view taken along the line IIII of Fig. 1;

Fig. 3 is a front view, partly in cross section, of the embodiment of. Fig. l with the parts thereof in their relative positions when the bit blades have become excessively worn; and

Fig. 4 and Fig. -5 are front views of a modification of the embodiment of Fig. 1.

Referring to the drawing in which like numerals refer to like elements throughout, the embodiment shown in Figs. 1 to 3, inclusive, comprises a bit consisting of a body In and blades H and I2. The body l0 may be afiixed to the lower end of a drill stem l3 by any suitable means, such as threads, the said drill stem being of conventional design fluidly connectible with the source of drilling fluid under pressure. Body ill is provided with a hollow internal portion M in fluid communication with drill stem II when drill stem [3 is connected with body 10. Ducts l5 and I6, conventionally termed eyes or water courses, fluidly connect the hollow portion [4 of body I 0 with the outer surface of said body, the outer terminus of ducts l5 and I6 being above the upper edge of bit blades H and I2, respectively, and normally directed in front of the cutting edges l1 and I8, respectively, of said blades. Bit blades H and I2 may be of any desired design and preferably are made of hard, tough, metallic materials. Th reaming edges 3 I9 and 20 of bit blades II and I2, respectively, are approximately parallel to each other and to the longitudinal axis of body I0. Cutting edges 2| and 22 of bit blades II and I2, respectively,

' may be perpendicular to the axis of body I8 though they may taper outwardly and downwardly as shown in the drawing. The cutting edge I8 of bit blade II is disposed approximately 180 from the cutting edge It of bit blade I2. Bit blades II and I2 may be incorporated into the lower end of body I8 in an suitable manner and are normally affixed to the said body by welding. The drawing shows a dual-bladed bit for the sake of simplicit although it will be understood that the bit of my invention ma have a greater number of blades.

The structure heretofore described is conventional to ordinary drag bits. In accordance with the present invention, the aforedescribed structure is modified by providing means within the bit body for closing at least one but not all of the water courses to the passage of drilling fluid when the bit blades have become worn by a predetermined amount during drilling operations. The drawing shows two water courses, namely I and I6, with means mounted in the bit body for closing water course I6 to the passage of drilling fluid when blades H and I2 have been worn by a pre-determined amount. The aforesaid means consists of a cylindrical duct 23 extending through bit body It and fluidly connecting internal hollow portion I4 with the outer surface of bit body I0. Duct 23 is positioned in body Ill so that its outer terminus is located in body I0 adjacent the face 24 of bit blade I2, which is oppo- I site the cutting face I! thereof. Duct 23 consists of an enlarged cylindrical portion 25 and a smaller cylindrical portion 26, the juncture of these two portions forming inwardly extending shoulder 21. Mounted within cylindrical portion 25 of duct 23 is piston 28 which is arranged to fit slidabl therein. Mounted on piston 28 is sealing ring 29 which provides a fluid-tight seal between piston 28 and the walls of enlarged portion 25 of .duct 23. Piston 28 is mechanically connected to a retaining ring 38 by means of piston rod 3|. Retaining ring 38 and consequently piston 28 is biased upwardly by means of spiral spring 32 which abuts against the ring 30 and shoulder 21. Piston stops 33 project into duct 23 and limit the downward movement of piston 28. Piston 28 defines a recess 34 in its side wall while duct 23 also carries a matching recess 35, recesses 34 and 35 being adapted to receive a shear pin 33 made of suitable metallic material. Duct 23 also defines near its upper end grooved recess 31, while piston 28 carries expansible ring 38 which is adapted to expand into recess 3! when piston 28 is so positioned in duct 23 that expansible ring 38 is opposite recess 31.

The outer end of portion 28 of duct 23 is normally sealed against, the passage of fluid therethrough by anysuitable means and may be closed by means of a plug 39, preferably of metal, to which is alfixed on its inner end sealing diaphragm 40. Sealing diaphragm 43 may be made of any suitable material which will provide a fluid-tight seal preventing the escape of fluid from duct 23 past plug 33. Synthetic rubber or natural rubber may suitabl be employed for this purpose. Plug 39 with sealing diaphragm 4n affixed thereto is normally held within portion 26 of duct 23 by means of rod M which is affixed to plug 39 and to blade I2 by suitable means. such as by welding. Rod AI is of" sufficient length to extend onto blade I2 to a point at least below the lower edge 49 of body 58. The highest point along blade I2 at which rod 4| is welded thereto will be the point atwhich bit wear is indicated, as will be hereinafter more fully described. Rod M may also be positioned in close proximity to the reaming edge 28 of bit blade I2, if desired, so as to indicate the point at which the bit has become worn out of gauge, as will also be more fully described hereinafter.

Sealing flapper 42, which is so constructed as to present a face 48 adapted to seal the inner end of duct I8 and which may be suitably made of hardened rubbery material or a satisfactory substitute therefor, is connected .by rod member 43 to a pivot 44 located on the inner surface of bit body It for arcuate movement about pivot 44. Rod member 43 carries a link 45 by means of which rod member 43 is mechanically connected to link 46 carried by the head of piston 28 through linked connecting member 41. Flapper 42, rod 33 and pivot 44 are so positioned with respect to duct I6 that when flapper 42 is moved arcuately and downwardly by downward and outward movement of piston 28, the face 48 of flapper 42 will cover the inner terminus of duct I8 and prevent the passage of drilling fluid from the.

interior hollow portion Id of body I8 to the ex--' terior of the said body.

In order to prevent any substantial downward movement of piston 28 induct 23, while plug 39 is in place in portion 26 of duct 23, the space between piston 28 and plug 39 is filled with a suitable liquid which may be lubricating oil or any other substantially non-compressible fluid which will remain in a liquid state while the device of my invention is in use.

The structure of my invention having herein before been fully described, its mode of operationi will now be briefly indicated. Fig. l or the draw ing shows the device of my invention in the posttion it assumes during normal drilling operations before the bit blades II and I2 have been worn to the point at which replacement is required. Fig. 3 shows the position of the device of my invention after the bit blade has been worn to a point to which the bit should be replaced.

Referring first to Fig. 1, it will be noted that flapper 42 is in a position out of contact with the inner terminus of duct I8 while piston 28 is positioned near the upper inner end of portion 25 of duct 23 and are so held by reason of the upward bias exerted by spring 32. Piston 28 may be further held against both upward and downward movement by means of shear pin 38. Thus, flapper 48 is maintained in a substantially upright position out of contact with the inner terminus of duct it until bit blades II and I2 are worn to a point as indicated in Fig. 3, at which time that portion of rod AI welded to blade I2 will also be worn off, thus permitting plug 36 and sealing material 4| attached thereto to be forced out of portion 26 of duct 23 by reason of the downward pressure exerted by the drilling fluid against the head of piston 28. Of course, shear pin 38 is made of a material which will shear when plug 39 and material 4| are removed from their normal position closing duct 23. Pis-'- ton 28 then moves downwardly in portion 25 of duct 24 until its lower edge abuts against stops 33, at. which time flapper 48 is carried against the inner terminus of water course I6, thereby closin same to the passage of drilling fluid as shown in Fig. 3. With water course I6 so closed, the

total nozzlearea of the bit'is markedly decreased and consequently the pressure of the drilling fluid in portion 'Mof bit body it and in drill stem i3 is markedly-increased, thereby indicating to thedrilling crew that the drill bit has been worn by "the pro-determined amount and requires replacement. The drill stem and bit may then be removed from the hole and while being withdrawn fluid may be circulated through duct 5. However, if it is desired to maintain maximum circulation through the drill stem while it is being withdrawn from the hole, flapper 33 may be -removed gfrom its position covering duct -16 so that drilling fluid may flow through this duct as 'well as through duct 85. The uncovering of duct It may be accomplished by shutting off the mud pumps maintaining the drilling fluid in drill stem l 3 under pressure, at which time the pressure inside drill stem '13 will be equalized with the pressure surrounding the drill stem. With the equalization of these pressures, spring :32 :driwzes piston 28. upwardly until expanding ring 33 is moved adjacent recess 3?, at which time ring 33 will engage in recess 3? and prevent further upward -,or downward movement of piston 28, With piston 28 in this position, flapper 48 again assumes a position which permits drilling fluid to flow through duct 6.

Instead of employing the means shown in Fig. 1 for sealing portion 26 of duct 23 and for indi cating bit wear, the arrangement shown in Figs. 4 and 5 may be employed in which outer end portion 26 of duct 23 is shown as being sealed against the passage of fluid therethrough by means of a tube 50 fluidly connected at its upper end with portion 26 and closed at its lower end 5|. The walls of tube 50 are afiixed to the walls of portion 26 of duct 23 and tube as is afiixed to blade l2 by suitable means, as by welding. The lower end 5| of tube 59 extends downwardly along blade I2 to a point at least below the'lower edge 49 of body I0. Tube 50 may also be positioned on blade l2 in close proximity to reaming edge thereof, if desired. Tube 50 and the space in duct 23 below piston 28 is filled with a substantially non-compressible fluid which will remain in the liquid state while the device of my invention is in use. A lubricating oil may be suitably used.

When the modification of Fig. 4 is employed, wear of bit blades l l and !2 during drilling eventually exposes lower end 5| of tube 50 to wear and opens it to the passage of fluid. If tube 50 is positioned in close proximity to the reaming edge 20 of blade I2, tube 5B'may be opened to the passage of fluid if the bit blades are worn out of gauge. When tube 58 is open to the passage of fluid trapped below piston 28, piston 28 moves downwardly and outwardly and flapper 48 closes duct [6 as hereinbefore described indicating to the drilling crew that the drill bit should be replaced.

While the drawing illustrates a drill bit having only one mechanism for closing one water course, it will be understood that the device of my invention may be modified to include a plurality of mechanisms similar to that shown, each mechanism being adapted to close one water course. Ordinarily, however, it will be found satisfactory to provide only one such mechanism as shown.

It is obvious that various changes may be made in the device hereinbefore illustrated and described without departing from the spirit of the invention or the scope of the annexed claims.

What I wish to claim as new and iuse'ful'an'd 'desire to secure by "Lettersl-Patent is:

seal closing the -outer terminus of said second duct adapted -to be removed by cutter blade wear, --a piston slidably mounted in said second duct for movement from arearward position to a forward position, means normally maintaining said piston in its rearward position, and a closure member mounted in the interior of said body and mechanically connected to said piston, said closure member being held in a position leaving said first "ducts open and unobstructed when said piston is in its rearward position and being movable o closeone of said first ducts upon movement of said piston from its rearward to its forward position upon removal of said seal.

2. A device in accordance with claim 1 in gvhiich said seal is a plug arranged in said second 3. A device in accordance with claim 1 in which said seal is a tube with its upper end in fluid communication with the outer terminus of said second duct having a closed lower end disposed in the path of cutter blade wear and sealing sald second duct against the passage of fluid therethrough.

4. A drill bit comprising, in combination, a hollow body releasably connectible with a drill stem to a source of drilling fluid under pressure provided with cutter blades on the lower end thereof, each of said blades having a cutting face, the body being supplied with at least one first duct for each blade fluidly connecting the inter1or of said body with the exterior of said body above said cutter blade and ahead of the cutting face of said blade, said body having at least one second duct fluidly connecting the interior of said body with the exterior of said body above said cutter blades and to the rear of the cutting face of said blades, a seal closing the outer terminus of said second duct adapted to be removed by cutter blade wear, a piston slidably arranged within said second duct, said piston being arranged to assume a first position, a second and a third position, a shear pin normally maintain ing said piston in its first position, a spring arranged within said second duct to bias said piston to its third position and a closure plate pivotally mounted in the interior of said body and mechanically connected to said piston, said closure plate being arranged to assume a first position leaving an open flow area to said first ducts when said piston is in its first position and movable to a second position preventing flow through one of said ducts when said piston moves from its first to its second position and movable to a third position leaving a flow area to said first ducts when said piston is in its third position.

5. A device in accordance with claim 4 in which the seal is a plug arranged in said second duct to close the outer terminus thereof.

6. A device in accordance with claim 4 in which said seal is a tube in fluid communication at its upper end with the outer terminus of said stem to a source of drilling fluid under pressure provided with cutter blades on the lower end thereof, each of said blades having a cutting face, the body being supplied with at least one first duct for each blade fluidly connecting the interior of said body with the exterior of said body above said cutter blade and ahead of the cutting face of said blade, said body having at least one second duct fluidly connecting the interior of said body with the exterior of said body above said cutter blades and to the rear of the cutting face of said blades, said second duct defining an annular recess adjacent its inner terminus,- a seal closing the outer terminus of said second duct adapted to be removed by cutter blade wear, a piston slidably arranged within said second duct, said piston being arranged to assume a first position, a second and a third position, a shear pin normally maintaining said piston in its first position, a spring arranged within said second duct to bias said piston to its third position, an expansible annular ring carried by said piston and adapted to expand into the annular recess defined by said second duct for locking said piston in its third position and-a closure plate pivotally mounted in the interior of said body and mechanically connected to said piston, said 010- sure plate being arranged to assume a first position leaving an open flow area to said first ducts when said piston is in its first position and movable to a second position preventing flow through one of said first ducts when said piston moves from its first to its second position and movable to a third position leaving a flow area to said first ducts when said piston is in its third position.

WALTER J. BIELSTEIN.

REFERENCES CITED n The following references are of record in th file of this patent:

UNITED STATES PATENTS Thrift et al NOV. 29, 1949 

